Tunable Elliptical Split Ring Resonator Using Single Varactor Diode for filter applications

The scope of this paper is to examine the effect of changing the structure of split ring resonator SRR from circular to an elliptical shape. The theoretical analysis of circular SRR (CSRR) is first examined and its results are compared with the simulated ones. Comparison between both configurations is also introduced. The new elliptical SRR (ESRR) can be adapted to operate in a multi-range of frequencies. The effect of gap position in ESRR resonant is also examined. When both gaps are moved but still aligned, the resonant frequency still the same. But when single gap is moved only the resonant frequency in changed to reach its maximum value when both gaps are in the same position. Frequency tunability can be offered by loading only a single varactor diode between the ESRR's metallic rings. The resonant frequency of the ESRR can be controlled by varying the capacitance of the varactor diode. Finite Element Method FEM is used to simulate the proposed structures using Ansys HF SS. A prototype of band notched coplanar waveguide filter loaded with single reconfigurable ESRR is fabricated and measured. A 0.5 F-p single capacitor element is used instead of using varactor diode and the measured S-21 is compared with the simulated results. Very good agreement has been obtained between them. A 5.6 GHz and 5.4 GHz notch frequencies in the filter operating frequencies are obtained using ESRR without and with varactor loading, which covers WLAN band.